Javascript

I am currently reading Smooth CoffeeScript which is a wonderful introduction to CoffeeScript.
Two PDF versions are available: with and without solutions to exercices, and there is also an interactive version which can be browsed directly. Other resources are available, e.g. JavaScript Basics.
I found this book thanks to a post by Karl Broman (who also has a very nice website full of interesting resources for those interested in statistics, genetics, and programming language).